Burglar-alarm.



0. L. DAVIS.

BURGLAR ALARM.

APPLICATION FILED PEB.21,1912

1,029,281, Patented June 11,1912.

OTIS L. DAVIS, OF IOWA CITY, IOWA.

BURGLAR-ALARM.

Specification of Letters Patent.

Application filed February 21, 1912.

Patented J true 11, 1912.

Serial No. 679,070.

To all whom it may concern:

Be it known that I, OTIS L. DAVIS, a citizen of the United States, residing at Iowa City, in the county of Johnson and State of Iowa, have invented a new and useful Improvement in Burglar-Alarms; and I do hereby declare the following, when taken in connection with the accompanying drawings and the characters of reference marked thereon, to be a full, clear, and exact description of the same, and which said drawings constitute part of this application, and represent, in

Figure 1 a vertical diagrammatic view, partly in section, showing the door closed. Fig. 2 a diagrammatic view partly in trans verse section of the same. Fig. 3 a view similar to Fig. 1 showing the door open. Fig. 4 a view similar to Fig. 2 showing the door open.

This invention-relates to an improvement in burglar alarms for doors, and particularly to alarms which are set in operation by the opening of the door, the object of the invention being to provide a simple arrangement of parts whereby the alarm is concealed from view, and yet ready for operation; and the invention consists in the construction and combination of parts as will be hereinafter described and particularly recited in the claim.

In carrying out my invention, I locate a cup-like shell 2 in the door casing 3 in line with one of the screw holes of the hinge; preferably if the hinge has three screw holes, with the center screw hole 4. This shell is set into the casing so that its outer end will stand at a point slightly beyond the inner face of the leaf 5 of the hinge when in place. In this shell is located a sleeve 6 formed from metal and adapted to contact with the inner face of the shell, and located in this sleeve and tightly fitting the same, is a plug 7 of insulating material into which the screw 8 is turned, the head of this screw fitting the screw hole 4. Within the shell and bearing against the inner end of the plug and tending to force it outward, is a spiral spring 9. The shell 2 is connected by a wire 10 with a suitable alarm bell 11 located at any suitable point, while the leaf 5 of the hinge is connected by a wire 12 through a battery 13 with the bell, these wires being run through the casing and hence concealed. lVhen the door is closed the screw 8 will be moved inward so as to crowd the plug 7 rearward and hold the sleeve 6 out of engagement with the inner face of the hinge.

plug outward and bring the outer end of the sleeve in contact with the inner face of the hinge so as to close the circuit and sound the alarm. With the low voltage usually employed in these alarms, the moving of the screw is very slight, so that when the door is opened, the fact that the screw is not perfectly seated in the hinge will not be apparent. It is understood, without illustration that suitable switches will be provided for cutting out the alarm when it is not desired.

I claim The combination with a hinge, of a shell adapted to be located in line with one of the screw holes in the hinge, a sleeve in said shell, an insulating plug in said sleeve, a screw passing through the hinge and into the plug, a spring between the shell and plug and tending to force the plug outward, an electric alarm, and wires connecting the shell and hinge with the alarm.

In testimony whereof, I have signed this specification in the presence of two subscribing witnesses.

OTIS L. DAVIS.

Witnesses:

HENRY G. WALKER, FRANG MooN.

Copies of this patent may be obtained for five cents each by addressing the Commissioner of Patents, Washington, D. G.

If, however, the, door be opened, the spring 9 will force the 

